java - Multicolumn ListView doesn't refresh using notifyDataSetChanged() -

i'm trying make listview using multicolumn format. found examples , have changed testing. want create list containg data bluetooth connection (and need preserve position when list updated).

my activity have list , button. clicking button list should show new values replacing first letters references numbers here happens:

list loaded:

after clicking button:

here code:

activity_main.xml

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" >  <listview     android:id="@+id/listview"     android:layout_height="wrap_content"     android:layout_width="match_parent"> </listview>  <button     android:id="@+id/btnok"     android:layout_width="100dp"     android:layout_height="wrap_content"     android:layout_gravity="center_horizontal"     android:text="ok"> </button> 

listview_row.xml

    <linearlayout android:id="@+id/relativelayout1" android:layout_height="fill_parent" android:layout_width="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android">  <textview     android:id="@+id/text1"     android:layout_width="0dp"     android:layout_height="wrap_content"     android:text="first"     android:layout_weight="1"> </textview>  <textview     android:id="@+id/text2"     android:layout_width="0dp"     android:layout_height="wrap_content"     android:text="second"     android:layout_weight="2"> </textview>  <textview     android:id="@+id/text3"     android:layout_width="0dp"     android:layout_height="wrap_content"     android:text="third"     android:layout_weight="1"> </textview>  <textview     android:id="@+id/text4"     android:layout_width="0dp"     android:layout_height="wrap_content"     android:text="fourth"     android:layout_weight="1"> </textview> 

mainactivity.java

public class mainactivity extends actionbaractivity {  private arraylist<hashmap<string, string>> list; private button btnok; private listview listview; private listviewadapter adapter;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      listview = (listview) findviewbyid(r.id.listview);      list = new arraylist<hashmap<string, string>>();      hashmap<string, string> temp1 = new hashmap<string, string>();     temp1.put("text1", "a1");     temp1.put("text2", "a2");     temp1.put("text3", "a3");     temp1.put("text4", "a4");     list.add(temp1);      hashmap<string, string> temp2 = new hashmap<string, string>();     temp2.put("text1", "b1");     temp2.put("text2", "b2");     temp2.put("text3", "b3");     temp2.put("text4", "b4");     list.add(temp2);      hashmap<string, string> temp3 = new hashmap<string, string>();     temp3.put("text1", "c1");     temp3.put("text2", "c2");     temp3.put("text3", "c3");     temp3.put("text4", "c4");     list.add(temp3);      adapter = new listviewadapter(this, list);     listview.setadapter(adapter);      btnok = (button) findviewbyid(r.id.btnok);      // create click listener     view.onclicklistener oclbtnok = new view.onclicklistener() {         @override         public void onclick(view v) {              // limpiar valor             list.clear();              hashmap<string, string> temp4 = new hashmap<string, string>();             temp4.put("text1", "11");             temp4.put("text2", "12");             temp4.put("text3", "13");             temp4.put("text4", "14");             list.add(temp4);              hashmap<string, string> temp5 = new hashmap<string, string>();             temp5.put("text1", "21");             temp5.put("text2", "22");             temp5.put("text3", "23");             temp5.put("text4", "24");             list.add(temp5);              hashmap<string, string> temp6 = new hashmap<string, string>();             temp6.put("text1", "31");             temp6.put("text2", "32");             temp6.put("text3", "33");             temp6.put("text4", "34");             list.add(temp6);              hashmap<string, string> temp7 = new hashmap<string, string>();             temp7.put("text1", "41");             temp7.put("text2", "42");             temp7.put("text3", "43");             temp7.put("text4", "44");             list.add(temp7);              hashmap<string, string> temp8 = new hashmap<string, string>();             temp8.put("text1", "51");             temp8.put("text2", "52");             temp8.put("text3", "53");             temp8.put("text4", "54");             list.add(temp8);              // actualizar             adapter.notifydatasetchanged();         }     };      // assign click listener ok button (btnok)     btnok.setonclicklistener(oclbtnok); }      @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.menu_main, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {     // handle action bar item clicks here. action bar     // automatically handle clicks on home/up button, long     // specify parent activity in androidmanifest.xml.     int id = item.getitemid();      //noinspection simplifiableifstatement     if (id == r.id.action_settings) {         return true;     }      return super.onoptionsitemselected(item); }  // adaptador para el listview private class listviewadapter extends baseadapter {      public arraylist<hashmap<string, string>> list;      activity activity;     textview txt1;     textview txt2;     textview txt3;     textview txt4;      public listviewadapter(activity activity,arraylist<hashmap<string, string>> list){         super();         this.activity=activity;         this.list=list;     }      @override     public int getcount() {         // todo auto-generated method stub         return list.size();     }      @override     public object getitem(int position) {         // todo auto-generated method stub         return list.get(position);     }      @override     public long getitemid(int position) {         // todo auto-generated method stub         return 0;     }      @override     public view getview(int position, view convertview, viewgroup parent) {         // todo auto-generated method stub          layoutinflater inflater=activity.getlayoutinflater();          if(convertview == null){              convertview=inflater.inflate(r.layout.listview_row, null);              txt1=(textview) convertview.findviewbyid(r.id.text1);             txt2=(textview) convertview.findviewbyid(r.id.text2);             txt3=(textview) convertview.findviewbyid(r.id.text3);             txt4=(textview) convertview.findviewbyid(r.id.text4);          }          hashmap<string, string> map=list.get(position);         txt1.settext(map.get("text1"));         txt2.settext(map.get("text2"));         txt3.settext(map.get("text3"));         txt4.settext(map.get("text4"));          return convertview;     } } 

just create single temp object , reuse ..may helps ..

list = new arraylist<hashmap<string, string>>();  hashmap<string, string> temp = new hashmap<string, string>(); temp.put("text1", "a1"); temp.put("text2", "a2"); temp.put("text3", "a3"); temp.put("text4", "a4"); list.add(temp);  temp.clear(); temp.put("text1", "b1"); temp.put("text2", "b2"); temp.put("text3", "b3"); temp.put("text4", "b4"); list.add(temp);  temp.clear(); temp.put("text1", "c1"); temp.put("text2", "c2"); temp.put("text3", "c3"); temp.put("text4", "c4"); list.add(temp);